Pressure equalizing and surge relief device for gun perforators



Dec. 6, 1938. w. T. WELLS 2,139,104

PRESSURE EQUALIZING AND SURGE RELIEF DEVICE FOR GUN PERFORATORS Filed Feb. 15, 1936 x0 5 a 12 s 7 13 1 .15 Z": Human/(m Patented Dec. 6, 1938 PRESSURE EQUALIZING AND SURGE REIJEF DEVICE FOR GUN PEBFORATORS wane: '1'. Wells, Glendale, cane, assignor, by mesne assignments, to Lane-Wells Company, Los Angeles, Call, a corporation of Delaware Application February 15, 1936, Serial No. 64,006

9 Claims. (01. 164-05) My invention relates to pressure equalizing and surge relieving devices and methods for gun perforators, and is particularly adapted for incorporation with gun periorators such as is disclosed in a copending application to one Wilfred G. Lane entitled Well casing perforator, Serial No. 734,- 171. This type 01' perforator comprises generally a body member having sockets which receive gun units. Space is provided around the inner ends of the gun units, and a passage extends along the length of the body to accommodate an ignition wire system. Difiiculty is encountered, particularly when the gun is submerged in liquid to great depths, in preventing seepage of the well liquid into the cavities of the body member which may result in damage to the wiring.

A primary object of the present invention consists essentially in subjecting the cavities of the body member to the same pressures that exist externally.

Another important object, along with the equalizing of pressure, is to minimize any peak or surge pressures caused by discharge of the gun units under liquid; the present application being a further development of my earlier Patent No. 2,029,454 issued February 4, 1936.

With the above and other objects in view as may hereinafter appear, reference is made to the accompanying drawing, in which:

Fig. l is a fragmentary, longitudinal, sectional view of a gun perforator incorporating my invention in its one form.

Fig. 2 is a similar fragmentary sectional view on a reduced scale of a modified. form of my invention with parts and portions shown in section and the device shown submerged in well liquid.

The well casing perforator with which my present invention is incorporated comprises a series of body elements I having externally threaded nipples 2 at their upper ends and internally threaded sockets 3 at their lower ends. The several body elements define an axially extending bore 4 which is intersected at intervals by large, laterally disposed sockets 5. Each socket is threaded at its outer portion to receive a gun unit 1. Coacting shoulders 8 and 9 are provided in the socket and gun unit respectively between which is interposed a gasket.

The inner end ill of each gun unit is smaller than the socket to define a cup-shaped chamber ll. At the inner end of each socket is mounted a contact plate I2 engaged by a terminal l3 extending from the inner end of the gun unit 1. An ignition wire system 6 extends through the central bore 4 and around the gun units within The lowermost body element I screws into an adapter collar M which in turn joins to a length of tubing l forming a surge chamber. The lower end of the tubing 15 is constricted but is provided with an opening I 5 therein so that the interior of the several body elements I is exposed to the pressure existing within the well bore. The length of the tubing I5 is such that the resulting volume of air compressed by the hydrostatic head of the well liquid is greater than the total volume of the cavities in the body elements. so that the liquid level within the surge chamber always remains below the body elements.

When the gun units are fired the liquid, which must be displaced to permit passage of the bullet, is displaced into the surge chamber and thereby greatly minimizes the peak concussive pressure set up in the well liquid.

When the gun perforator is used with the foregoing device in wells of great depth, the surge chamber has considerable length and may constitute one or several stands of tubing. In practice, the tubing is first run in the well in the usual manner until its upper end protrudes; whereupon, the perforator gun is attached and the whole device is lowered. If several runs are required, the tubing may be held by slips while the gun is disconnected, serviced, and reconnected; or the gun may be serviced while connected to the tubing.

The surge chamber may be materially shortened by utilizing the arrangement shown in Fig. 2. In place of the adapter collar M, a cylinder I1 is substituted, and a relatively short hollow plug I8 is connected to its lower end. The cylinder ll receives a piston l9 preferably of yieldable material impervious to oil or other well fluid. Above the piston, the cylinder is partially filled with a quantity of insulating liquid 20. The volume of this liquid is preferably about twice the combined volume of the cavities within the body elements, and the volume of the cylinder is preferably more than twice the volume of the liquid 20. Thus,

when the piston is in its lower position, the pershifted to its lower position. For this purpose a ring 2| may depend from the piston which may be engaged by a hook, not shown, inserted through the bottom of the hollow plug ll before each run of the gun into the well bore.

In operation, the pressure of the surrounding liquid forces the piston upwardly, and a quantity of air 22 is entrapped below the plug. The entrapped air below the plug serves to cushion the concussive pressures resulting from discharge of the gun units. Y

My method of both equalizing pressure and relieving pressure surges consists essentially in exposing the interior of the gun perforator to the external pressures while isolating the interior from the external liquid itself.

Though I have shown' and described certain embodiments of my invention and a certain method of operation, I do not wish to be limited thereto but desire to include in the scope of my invention the constructions, combinations, and arrangements embraced in the appended claims.

I claim:

1. The combination with a gun type perforator adapted to fire projectiles while submerged in liquid and employing a hollow body member containing elements subject to damage from well liquids of: a tube depending from said body member and communicating with the interior thereof, said tube being open at its lower end; and an air chamber within said tube below said body member and responsive to hydrostatic pressures externally of the body member to exert a balancing pressure within said body member.

2. The combination with a gun type perforato-r adapted to fire projectiles while submerged in liquid and employing a hollow body member containing elementssubject to damage from well liquids of an open ended tube depending from said body member and exposing the interior of the body member to well pressure; and an air cushion within said tube below said body member, said air cushion having a volume in suificient excess of the well liquid displaced by discharge of a projectile fired from the perforator to absorb the same without material increase in pressure therein and positioned to apply the well fluid pressure against the interior of said body memher.

3. In a gun type perforator: a hollow body member having a longitudinal bore therethrough and lateral'socke'ts intersecting said bore; gun units removably secured in said sockets, each gun unit adapted to fire a projectile; ignition wiring in said bore and connected with the several gun unitsfand means defining a. passageway for exposing the interior of said body member to the pressure exerted by the well liquid in which the body member is immersed and means for isolating the ignition wiring therein from contact therewith.

4. In a gun type perforator: a hollow body member having a longitudinal bore therethrough and lateral sockets intersecting said bore; gun units removably secured in said sockets, each gun unit adapted to fire a projectile; an open ended tube depending from said body member and exposing the interior thereof to well pressure; and an air chamber therein separating the interior of the body member from well liquid entering the bottom of the tube and positioned to apply the well pressures against the interior of said tube.

5. In a gun type periorator: a hollow body member having a longitudinal bore therethrough and lateral sockets intersecting said bore; gun units removably secured in said sockets, each gun unit adapted to fire a. projectile; a. surge chamber depending from said body member for absorbing concussive pressures set up by discharge of said gun units; a floating piston defining the upper end of said surge chamber, and a non-conductive liquid above the piston adapted to be forced into said body member to balance the pressure therein against the hydrostatic pressure 01' the liquid in which said body member is immersed.

6. A gun type perforator comprising: a. hollow body member having a. longitudinal bore therethrough and lateral sockets intersecting said bore; gun units removably secured in said sockets, each gun unit being adapted to fire a projectile; means in said sockets and bore connecting the several gun units with a controlling instrumentality, said means being subject to damage from contact with well fluid; a surge chamber depending from said body member exposed to the interior thereof and open at its lower end; and an air cushion incorporating at least a portion of said surge chamber for subjecting the interior of said body member to the pressure of the liquid in which it may be immersed while isolating said passage from contact with said liquid.

7. A gun type perforator comprising: a body member having a. conduit passage therein open at its lower end and laterally directed sockets intersecting said passage; a plurality of gun units adapted to be sealed in said sockets; and means incorporating said passage for equalizing the pressure inside said body member with the well liquid in which it may be immersed.

8. A gun type perforator comprising: a body member having a conduit passage therein open at its lower end and laterally directed sockets intersecting said passage; a plurality of gun units adapted to be sealed in said sockets; and means incorporating said passage for equalizing the pressure inside said body member with the well liquid in which it may be immersed, said equalizing means including an air chamber for cushioning the pressure surges due to the firing of said gun units.

9. The combination. with a gun type perforator adapted to fire projectiles while submerged in a liquid and employing a hollow body member containing elements subject to damage from contact with well liquids of: means subjecting the interior of the body member and the elements thereinto the pressure exerted by the well liquid, thereby eliminating pressure differential between the interior and exterior of said body member; and means for isolating said elements from actual contact with said liquid.

WALTER T. WELLS. 

